Adam Yauch, one-third of the pioneering hip-hop group the Beastie Boys, has died at the age of 47, Rolling Stone has learned. Yauch, also known as MCA, had been in treatment for cancer since 2009. The rapper was diagnosed in 2009 after discovering a tumor in his salivary gland.

“It is with great sadness that we confirm that musician, rapper, activist and director Adam ‘MCA’ Yauch, founding member of Beastie Boys and also of the Milarepa Foundation that produced the Tibetan Freedom Concert benefits, and film production and distribution company Oscilloscope Laboratories, passed away in his native New York City this morning after a near-three-year battle with cancer,” reads an official statement from the Beastie Boys. “He was 47 years old.”

Yauch sat out the Beastie Boys’ induction to the Rock and Roll Hall of Fame in April, and his treatments delayed the release of the group’s most recent album, Hot Sauce Committee Part Two. The Beastie Boys had not performed live since the summer of 2009, and Yauch’s illness prevented the group from appearing in music videos for Hot Sauce Committee Part Two.

Yauch co-founded the Beastie Boys with Mike “Mike D” Diamond and Adam “Ad-Rock” Horovitz in 1979. The band started off as a hardcore punk group, but soon began experimenting with hip-hop. The band broke huge with their first proper album, Licensed to Ill, in 1986; it was the biggest-selling rap album of the decade and the first to reach Number One on the Billboard chart. Further albums Paul’s Boutique, Check Your Head and Ill Communication cemented the Beasties as a true superstar act.

In addition to his career with the Beastie Boys, Yauch was heavily involved in the movement to free Tibet. A founder of the Milarepa Fund, Yauch was instrumental in the first Tibetan Freedom Concert in San Francisco’s Golden Gate Park 1996, which drew 100,000 people – the largest U.S. benefit concert since 1985’s Live Aid. After 9/11, Yauch and the Beastie Boys organized New Yorkers Against Violence, a concert benefit for some of the victims least likely to receive help from elsewhere.

Yauch also directed many of the Beastie Boys’ music videos under the pseudonym Nathaniel Hornblower. In 2002, he launched the film production company Oscilloscope Laboratories. As a filmmaker, he directed the 2006 Beastie Boys concert film Awesome; I Fuckin’ Shot That! and the 2008 basketball documentary Gunnin’ for That #1 Spot, and his production company released the acclaimed Banksy movie Exit Through the Gift Shop.